2200 fuel injected check engine light question

hey guys, 91 2200 fuelie check engine light only comes on at idle. as soon as you touch the gas it goes off and stays off until you let of the pedal all the way. the truck also has a high idle all the time. any ideas? i thought intake gasket but with carb cleaner io couldnt find anything.

for that matter how do i check the engine light code? i know on chevys you can jump a few pins on the port and it will flash out.

disconnect the (-) on your battery for about 20 minutes and see if that clears it out.

i don't think disconnecting the battery will make it go away if it only happens at idle...have some one read the codes with a scanner..the problem is gonna be something that only happens at idle..does it misfire? idle high or low?